Money or smiles: Independent ERP effects of associated monetary reward and happy faces

In comparison to neutral faces, facial expressions of emotion are known to elicit attentional prioritization, mainly demonstrated by means of event-related potentials (ERPs). Recent evidence indicated that such a preferential processing can also be gained by neutral faces when associated with increased motivational salience via reward. It remains, however, an open question, whether impacts of inherent emotional salience and associated motivational salience might be integrated. In the present study, participants (N=42) learned to categorize happy and neutral faces as reward- and zero-outcome-related via an associative learning paradigm. After successful learning, a consolidation phase followed to strengthen the learned associations. ERPs were recorded throughout the experiment. In the learning phase, happy faces boosted the face-sensitive N170 and the emotion-related EPN component, compared to neutral faces, whereas effects of associated motivational salience were absent. In the subsequent consolidation phase, happy faces again elicited enhanced N170 and EPN amplitudes, while reward-associated faces -- irrespective of their expressions -- amplified the LPC, a component linked to higher-order evaluations. Interactions between expressions and associated outcome conditions were absent in all ERP components of interest. The present study offers new evidence that acquired salience impacts stimulus processing but independent of the effects driven by happy facial expressions.